i hesitate to say this because i know there are anti-lime nazis out there, but if that were my plant i would water it with a liquid lime solution or top dress with some finely powdered dolomite, wait a week, and check for healthy new growth.
i'm sure it would like a new pot as well, but IN MY OPINION if you don't correct the problem in the cup you'll never get a handle on it in the new pot. i plan on making a tutorial on this soon but i need a few more example pics and fucking up a plant just to make a tutorial isn't in the cards right now
liquid lime at 1 tablespoon per gallon OR a top dress of FINELY powdered dolomite and plain water. do not use agricultural lime or any other lime that is in chunks. understand it will take a week or so to do its thing, but your focus right now should be on GETTING HEALTHY NEW GROWTH.
if something is up with your soil or stock water, repotting is only going to delay the problem, not solve it. since the plant is stunted anyway, you are not "losing out" on growth time.
flame away, lime nazis.