While my V. Sansei Blue currently has 8 gorgeous flowers it also suffers from brown tips on some of the leaves.
Eventually the leaf dies. Could low humidity cause this?
Other cultural problems?
If the whole leaf is turning yellow that could be low humidity, too little light, not enough water or not enough fertilizer. But if just the tips are turning brown thats often caused by fertilizer burn. It could be from the fertilizer being too strong or from salts built up in root area. The solution there would be to flush the plant very well with plain water. Wait ten or fifteen minutes and flush it again. Good luck.