Epictetus does not speak about suicide, as far as I am aware, in either the Enchiridion or the Discourses. Epictetus himself did not die by suicide. He did have some physical-health problems (such as a limp) from his days as a slave, but I am not sure they contributed to his death. But it was not suicide, at any rate.

Seneca, of course, did kill himself: he was ordered to commit suicide at Nero's urging because he was charged with complicity in the Pisonian conspiracy to assassinate Nero. He had asked several times earlier in his career for Nero's permission to retire.

The Stoics generally accepted the moral permissibility of suicide from the earliest days of their movement: Zeno, a founder of Stoicism, and his successor, Cleanthes, committed suicide.

In Roman Stoicism, Cato the Younger, a Stoic, killed himself too, rather than condescend to have Julius Caesar pardon him.

The Stoics, therefore, might seem to have a suicide "problem" -- but we shouldn't make it sound like Stoicism was a suicide cult. And beside, they did not think that suicide was a real "problem" philosophically.

Seneca himself talks about how suicide grants people "freedom" (libertas). But even the earliest Greek Stoics thought that a wise person has the right to seek a "reasonable departure" (eulogos exagoge) from life.

However, this does not mean that "life is the same as death," as you put it. The Stoics did not think that we should be indifferent to everything. The Stoics thought that there were preferred and dispreferred indifferents. Virtue is the only unqualified good thing, and vice is the only unqualified bad thing, but this does not mean that everything else is "the same." If I offer a virtuous person millions of dollars at (truly!) no cost or nothing, and their virtue is not being risked at all, the virtuous person should prefer the millions of dollars. The same goes for health and life: if your health and life aren't coming at the cost of your virtue, you should choose to be healthy. But if your health and life start interfering with your ability to live virtuously, you should prefer to die.

That makes sense of the Stoic position on suicide. As Diogenes Laertius reports:

"[The Stoics] say that the wise man will commit a well-reasoned suicide both on behalf of his country and on behalf of his friends, and if he falls victim to unduly severe pain or mutilation or incurable illness" (7.130).

It is hard to say, then, that the Stoics had a suicide "problem" and definitely Seneca would not have urged people to stop committing suicide. He thought it granted us freedom, and he himself committed suicide.