Vanda leaf tips yellowing then dying

[TMallanjr]

Hi everyone, I am hoping you guys can give me some help with my Vanda "Legacy Black". Bought 2.5 yrs ago from local grower (NJ) and was doing great, sprouting new leaves and bloomed 2x since then but this problem just started this winter. I grow them outside in the summer and move inside on a SW facing window ledge in the winter getting 4-ish hrs sun. 5 leaves so far have started turning yellow at the tips and discoloration works its way back to the stem followed by browning then dropping off. (see pics) I have had a bunch of Cattleyas for years with good success but am new to Vandas. Feed Tezula Plants "MSU Fert" 13-3 15 @ half strength weekly and try to soak the plant in a bucket of water for 2 minutes at least every other day. Just noticed the black root tip when taking the pics and after reading other posts here thought it might matter. Only 3-4 on plant with all other tips being nice healthy green. Any info you can give is greatly appreciated.