I set up my home darkroom for the first time last weekend, mixed my chemicals according to the directions, and started printing. Everything seemed to be going well. I made about four or five 8x10 test prints and about five 11x14 prints before I had to take a break. I closed the door to the bathroom, turned off the light, and after a couple hours came back and started working on another print. That one came out well. The one after that didn't want to develop at all. Only a very faint image appeared in some spots; the rest of the paper remained white. I assumed I had left the developer (Ilford Multigrade) sitting too long and decided to try again today, this time without any interruptions. Once again, after about five 11x14 prints, the developer seemed to be exhausted. I mixed up a bit more to see if I could stretch it out, but the addition of the new mixture didn't seem to make it work, either. The temperature of the developer was 65 degrees F, and it had a very slight yellowish tinge to it. I purchased all my chemicals last week at a local camera store. Judging by the way the guy at the register acted, not very many people buy chemicals from this store. I looked on the bottle to see if I could find an expiration date, but all I found was a batch number. Is it possible that I just purchased an expired bottle or is something else going on? The Ilford stop and rapid fixer I purchased along with the developer seem to be all right. I'm very careful about avoiding cross-contamination; all my trays and tongs are clearly marked. In the future, where is the best place to get developer?