Does Fertilizer Go Bad (& a couple other ?s)

[Mountaineer370]

Apologies in advance for more fertilizer questions. I have searched the forum to the best of my ability but I have not been able to find answers to these particular ones.

My orchid collection is small, only twenty-some plants. I have been using the MSU formula, but I find that even when I buy a small container, by the time I get around to using it up (maybe a year or more?), it has changed color and is stuck together in clumps. It does have the moisture-absorbing packet in it.

My first question is: Does fertilizer go bad after a time, or become less potent? Is what I have described an indication that the fertilizer has degraded in some way?

Second question: I have heard and read many times that we should only be using 1/4 or so of the recommended amount of fertilizer. For clarification, does this apply even when using fertilizer specifically formulated for orchids? Or maybe that reduced amount is meant to apply only to those who fertilize frequently (weekly, weakly), and if we are only fertilizing once or twice a month, the directions on the container are proper?

Finally: I have used up my current supply of MSU fertilizer and I'm reluctant to buy more since it takes me so long to use it up. I currently have in my cupboard the following liquid fertilizers, all Schultz brand:

Plant Food Plus, 10-15-10
African Violet Plus, 8-14-9
Cactus Plus, 2-7-7

Is it safe to use any or all of these on my orchids?