I Bought Yoghurt Culture To Make My Own Yoghurt

The other day I found a site that sells yoghurt culture which you can buy from here GreenlivingAustralia
I ordered it on Tuesday and it arrived on Friday . I bought the packet of culture that will make from 80 -100 litres of yoghurt and it cost me $14.95 .The recipe says to make one litre of yoghurt use 1 litre of milk I used full cream UHT milk a tiny bit of the culture and they say to make it thick use 1/3 cup of powdered milk. I don't use powdered milk so of course didn't have any so went without and the yoghurt was good, we had the yoghurt with our breakfast this morning. So milk costing $1 a litre and culture 15cents if it makes 100 litres , but I've decided to use a little more to save using powdered milk so it should cost me between $1.30 -$1.40 a litre . I'll be very happy with that, some thing I won't have to buy when shopping. You need to store the culture in the freezer. Today I started another batch by using 4 tablespoons of the previous batch, we will see how well it turns out and I may do it every second or third batch to make the culture last longer.I used my easiyo yoghurt maker and a one litre glass jar, I've never used the easiyo yoghurt mixes as they contain soy and other ingredients I don't want to eat.
I've made 3 batches of yoghurt and they have all turned out like glue, I'm not sure what I'm doing wrong but really not happy with the outcome at all... If any one can offer any advice I would really appreciate that.