Brassia new growth yellowing
 

Sections of the leaves of this most recent round of new growth is turning yellow before its even finished developing. I haven't had this issue with this plant before. Could this be fertilizer burn?

I would expect high mineral content to damage most leaves symmetrically, including older ones. If this is only on new growth I would wonder about underwatering. It appears to be inside a house so humidity probably isn't high enough for a fungal issue, though there are fungi that cause dieback from leaf tips.

has the watering changed?

Watering hasn't changed, no. I continue to grow it very wet as I always have. Also yeah this one is grown completely indoors where the humidity is only around 55%.

I used to run a humidifier, but stopped after I started growing all my high humidity plants outdoors.

On the off chance it's fungal, I would snip off the brown parts well into green tissue. Treat the blade with 70% alcohol or 10% bleach between snips.

Sounds good, I'll do that.

Also could root rot cause this? I don't know if I have any but I repotted into a bigger pot not too long ago so I wouldn't be surprised if there was some level of root rot.

Root problems would affect most or all leaves. I wouldn't repot again so soon.