welcome to GoY.
do you know which one it is you have? there are many species and varieties.

are they in semi shade or full sun? the ones I grow are shady ladies and have you been watering them?

Is the leaf loss on all stems, or just some of them, and did they flower this year? As seaburngirl asks, do you know which Euphorbias you have?

I think I have the Euphorbia Characias. They are one year old and bloomed last year, but not this year. They are in full sun. They were fine, however, no blooms and then all of a sudden it seems the leaves are falling off on all stems. One of the plants didn't grow as big as the other two. I was told that they were getting too much water, but I have a drip system and only water when I water my yard, about 45 min a day. I cut them down last winter like I was told. Not sure what to do now!! Thank you for your responses

Depending on where you live in the States, every day watering is probably way too often, and a drip system won't give enough water at a time in just 45 minutes. I'd need more info on your climate to give intelligent advice about watering, but right now, it looks like overwatering.

they prefer moist but well-drained soil, in full sun. So depending on where you are in the USA how well drained is your soil. They sound as if they are too wet.

general care is: is to cut down the flower stems to ground level as the blooms fade. Be careful when handling the plant as the thick, white sap can irritate the eyes and skin.
they are pretty tough plants so I suspect they will come back next year.

I live in western Oregon, USA. There is sufficient drainage and good soil. I haven't watered them for two days now.Thank you for your responses!

Note you should only cut down the flowered stems, not all the stems every year...

oh ok, thanks for the info!