Encyclia prismatocarpum leaf turning yellow..:(

[merytt]

Hi!
My encyclia leaf started turnung yellow for some reason and i cant figure out why..? It resently put up two new bulbs and looked great. Then littel less than 3 weeks ago. I cuty off the tip, then i repotted it couse i wanted to know what is bothering my sweetheart. On the top, bottom and on sides the substrate was dry, but omg how wet was it beneath roots:S I changed it, put half of the pot charcoal and FIBO gravel ( littel light balls u use for S/H culture) and then put medium bark te another half.
But now the leaf is still turning yellow!!! ohhh... And i just dont know why... I left to dry, and hatered it only last week. I water it when the pot is light, substrate feels dry. I fertilitize it very weekly, every other week.
Can you help, what could be wrong.