I'm not sure if you have them but I think every nurgle list should have at least a feculant gnarlmaw, generates d3 contagion points if you're good for summoning, but most importantly it allows you to run and charge in the same turn! Getting a second one is also great cause you can summon another one for 7 points to allow you to run and charge unexpectedly.
Other than that, picking up some plaguebearers (unit of 30 is amazing) for an anvil is fantastic but pricey, both on the wallet and points wise (320 for 30, 35 dollars for 10 models). But glottkin spell for plaguebearers is disgusting, 5+ save, 5++ feel no pain, -1 to hit, 2 wounds a piece? Good luck ripping through that. Combine a witherstave artifact for some truly tanky tarpits.
You have more than 2k points already so if you wanna use what you have, I think the feculant gnarlmaw is gonna be something that will change your forces threat distance by quite a bit! What you currently have is not a bad force at all!
If you're toying around with an idea, feel free to drop it here, I love my nurgle list but I run more daemon (so I could use it for 40k as well as AoS) so I haven't explored too much of the mortal side.
The battalion for blightkings is also something you might want to consider running, adds -1 rend to all of their attacks which is amazing. Plus they ignore cover!
If you want to run this battalion though, picking up a lord of blights would not be a bad idea, gives all of them a (weak) ranged attack to all blight king units within 3 inches.