The ink comes out wrong!
Some ways to deal with ink flow problems.
Several things could be occurring here.
Are the nibs you are using new?
Did you clean the nibs since the last time they were used?
Are you draining the nib after dipping but prior to using?
What kind of nibs are you using?
Is the nib your using new or almost new?
If the nibs you are using are new or mostly new you may be running into the problem of packaging oil. Almost all manufacturers put a protective layer of oil on their nibs. This oil must be removed before the dip nib can be used without having ink problems. The most common problem associated with a new nib is ink is the ink just all running off the nib.
There are two ways that I prefer to clean the oil off the nibs.
1 - Heat temper. Use any household candle. Put the nib into the point of the flame where the inner "no color" spot ends and the color spot begins. This is the hottest part of the flame. Keep the nib there running the entire nib through there for anywhere between 10 to 30 seconds. If the nib glows your done.
Immediately dip the nib into an adjacent container of water. This does two things. 1 - It gets rid of the oil rather quickly and it will temper you nib making it stiffer and more flexible at that same time.
Be careful not to over temper your nib. They bend if you do that and warped nibs don't write well or at all.
Second way that I do this.
For nibs that are smaller (anything less than a Mitchell 3.5) I prefer to use lemon juice. Lemon juice is acidic so you have to pay attention. My technique here is to put the nibs into a container of lemon juice just enough to cover the nibs. I let them sit over night, but no more than 10 hours. Then I thoroughly rinse the nibs in water and very carefully dry the nibs using a paper towel. Feel free to use something else. Inspect each one to make sure that there is no rust and that you didn't leave any particles of paper towel behind or other drying device.
Do not air dry. You will end up with rusty nibs this way. And rusty nibs are generally useless. I learned this lesson the hard way. Truly it was a forseeable outcome but now that the lesson is learned I won't make that mistake again.
Did you clean the nib after you used it last time?
If you didn't, well frankly, shame on you. That is generally very bad for you nib often causing pitting a rusting of the nib. Even if you escape those bad consequences an unclean nib makes clogs in your nib.
The anatomy of pen nib is important to know because that tells you how they work. Most dip pens have a reservoir. Reservoirs can be detachable or attached depending on the brand and make of the nib. If you inspect your nibs carefully you will find that they all have a crack in them. Some have multiple cracks in them. This is the capillary line and it is there on purpose.
The capillary line works to draw ink from the reservoir (or ink drop if there is no reservoir) to under the pen. This allows the ink to conform to the shape of the nib tip. Without this capillary line the ink moves down the nib in a much less controlled manner and the pen nib will merely push the ink around and the ink will flow around the nib not with it. This makes for less than crisp calligraphy strokes.
A clogged capillary can cause all sorts of problems. They can stop the flow of ink entirely. They can cause the ink to just blob onto your writing surface.
Clean your nibs after every use. Also inks can be acidic, neutral or basic. Don't take the risk of old ink ruining a good nib because you didn't clean the nib properly. Liquid soap, a toothbrush and tap water work fine for common inks. Not at all for lacquered inks or oil based inks. I use vodka or ethyl alcohol for those.
As always towel dry your nib to avoid rust.
Are you draining your nib after dipping but prior to use? Do you blot?
It is important to dip your nib appropriately and then drain it appropriately as well. Try to always dip you nib exactly half way from the tip to the nibs top. Try to never dip your pen much deeper than this. You can get into all sorts of trouble with the pen holder if you do that.
Once you dip your pen you will notice that here is almost always a little drop of ink extra that you don't need. If you don't get rid of this extra drop the ink will blob onto the paper. Getting rid of this extra drop is as easy as putting the bottom of the nib against the wall of the mouth of your ink vessel. It will drain the excess ink.
Then use a piece of scrap writing medium to draw some quick lines with the recently dipped nib. This is called blotting. Once they show up as crisp and clear with no blobbing, you're good to go!
What kind of nib are you using?
Each brand of nib has its own peculiarities as does the size of the nib from each brand. However the above issues and resolutions should help fix most problems associated with the nibs.