that was what i have been saying, but i dont think it's something a resource pack can fix.
no, it appears to be fully grown at stage 3 (second to last stage), and mature crops have the same texture as freshly planted n-wart. basically, freshly planted wart is indecipherable from fully grown.
I would like to add that the nether wart appears to show stage 4 texture at stage 3, rather than keeping the same texture as stage 2, then loops around.
I'm off to fill some chests with rails